fn main() {
    let s = "a,b,c".to_string();
    let mut it = s.split(",");
    let mut it2 = it.clone();
    it.for_each(|mut e| {
        e = "1";
    });

    it2.for_each(|c| {
        println!("{}", c);
    });

    println!("{}", s);

    let v = vec![1, 2, 3];
    let maybe = (v.len() > 3).then(|| v);
    println!("{:?}", maybe);
}
